UC-NRLF 


8061' IZ 


OH;  s 


The  Time  Factor  in  Making 
Oil  Gas 


DISSERTATION 


SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 

FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY 

IN  THE  FACULTY  OF  PURE  SCIENCE 

COLUMBIA  UNIVERSITY 


BY 
Clive  Morris  Alexander,  B.S.,  M.S. 


NEW  YORK  CITY 
1915 


The  Time  Factor  in  Making 
Oil  Gas 


DISSERTATION 


SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 

FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY 

IN  THE  FACULTY  OF  PURE  SCIENCE 

COLUMBIA  UNIVERSITY 


BY 
Clive  Morris  Alexander,  B.S.,  M.S, 


NEW  YORK  CITY 
1915 


ESCHENBACH  PRINTING  COMPANY 

EASTON,  PENNA. 

1915 


0 


ACKNOWLEDGMENTS 

The  author  desires  to  express  his  sincere  gratitude 
to  Professor  Milton  C.  Whitaker,  at  whose  suggestion 
and  under  whose  direct  supervision  this  investigation 
was  carried  out. 

Thanks  are  also  due  to  Professors  S.  A.  Tucker  and 
F.  J.  Metzger  for  their  advice  in  this  work. 

C.   M.  ALEXANDER 

CHEMICAL  ENGINEERING  LABORATORY 

COLUMBIA  UNIVERSITY,  NEW  YORK 

MAY,  1915 


343670 


THE  TIME  FACTOR  IN  MAKING  OIL  GAS 

The  production  of  oil  gas  is  dependent  upon  certain 
chemical  laws  which  relate  to  gas  reactions  in  general 
and  which  embody  the  principles  of  both  thermody- 
namics and  chemical  kinetics. 

In  an  investigation  on  the  effect  of  the  variables, 
temperature,  pressure,  and  concentration  on  the 
thermal  decomposition  of  petroleum  and  petroleum 
distillates,  Whitaker  and  Rittman1  have  carefully 
considered  the  theoretical  principles  of  thermodynamics 
as  applied  to  gas  reactions.  Their  experimental  re- 
sults verified  their  theoretical  conclusions  and  showed 
that  the  principles  of  thermodynamics  apply  to  the 
decomposition  of  petroleum  hydrocarbons  as  well  as 
to  more  simple  reactions. 

In  the  above  work,  however,  conclusions  were  drawn 
on  the  assumption  that  chemical  equilibrium  was 
attained  under  the  experimental  conditions  adopted. 
It  then  became  a  question  whether  or  not  equilibrium 
was  reached.  Undoubtedly  this  question  could  be 
answered  by  the  application  of  the  principles  of  chemi- 
cal kinetics,  which  introduced  the  time  factor.  In 
the  present  study  of  oil  gas  production,  therefore,  four 
variables — time,  temperature,  pressure  and  concentra- 
tion— are  recognized. 

Difficulties  were  foreseen,  however,  in  the  accurate 
adjustment  of  the  above  variables  in  commercial 
plants  and  a  basis  for  control  was  sought  which  would 
fall  within  the  range  of  engineering  requirements. 
Under  constant  temperature  and  pressure  conditions, 
the  time  factor,  which  can  be  controlled  by  variation 
of  the  rate  of  oil  feed,  offers  the  most  available  means 
for  the  study  of  the  thermal  decomposition  of  pe- 
troleum and  petroleum  distillates  on  the  basis  of  the 
principles  of  chemical  kinetics. 

Design  of  apparatus  is  fixed  for  any  one  construction 
and  hence  remains  a  constant  factor  while  the  varia- 
bles are  controllable  within  certain  operating  limits. 

»  J.  1.  E.  C.,    6  (1914),  383,  472. 

(I) 


The  concentration  factor  above  is  considered  in  the 
sense  of  changes  involved  in  the  admixing  of  other  sub- 
str.nces  whh  the  initial  material,  such  as  the  decomposi- 
tion of  oil  in  an  atmosphere  of  hydrogen,  carbon  mon- 
oxide, etc. 

THEORETICAL 

According  to  chemical  kinetics,  a  reaction  tending 
toward  a  state  of  equilibrium  will  require  time  to 
reach  such  a  state. 

A  reversible  reaction  may  be  represented  thus: 
WiAi  +  »2A2^±:wi/Ai'  +  »2'A2'.  .  . 

Such  an  equation  represents  two  reverse  reactions, 
each  with  a  separate  reaction  velocity: 

v  =  £(Ai)Wl(A2)W2.  .  .  v'  =  £'(AiT''(A2')n2'.  •  • 

The  difference  between  these  two  velocities  at  any 
moment  of  time  under  constant  conditions  will  give 
a  certain  change  per  unit  of  time  in  one  direction  or 
the  other  toward  equilibrium.  This  change  per 

increment  of  time,  —  .  is  commonly  shown  as  follows: 
at 


at 

in  which  k  and  kr  are  the  velocity  constants  of  the  two 
reverse  reactions,  (Ai),  (A2),  etc.,  are  the  concentrations 
of  the  reacting  substances,  and  »i,  w2,  etc.,  their  re- 
spective molecular  exponents  as  obtained  from  a 
properly  balanced  equation. 

The  above  velocity  constants  vary  with  temperature1 
and  as  a  result  temperature  has  a  very  marked  effect 
upon  the  reaction  velocities  of  the  two  reverse  reactions. 
The  effect  of  temperature  on  a  number  of  gas  reactions 
has  been  very  carefully  studied  by  Bodenstein2  and 
the  fundamental  equations  applied  mathematically 
to  the  experimental  results. 

At  equilibrium,  the  velocities  of  the  opposing  re- 
actions are  equal  and  hence  the  change  per  increment 

of  time,  —  ,  must  become  zero. 
at 

—  =  v—v' 

k     (AiT'CA,')1*'...    -, 

Hence'  = 


i  Trautz.  Z  Eleklrochem.,  18  (1912),  513;  Z.  pkysik.  Chem.,  68  (1909). 
295;  74  (1910).  747;  Zellinek,  Z.  anorg.  Chem.,  49  (1906),  229. 

*  Bodenstein,  Z.  physik.  Chem..  29  (1899),  147,  295,  315,  429,  665; 
Bodenstein  and  Wolgast,  Ibid.,  61  (1908).  422. 

(2) 


where  K  is  the  equilibrium  constant.  Thus  chemical 
equilibrium  deals  only  with  the  end  state  of  a  reaction 
and  time  is  not  a  factor. 

Where  time  is  not  considered  the  relations  between 
the  state  of  equilibrium  and  the  thermal  values  of  a 
reaction  can  be  worked  out  by  the  application  of 
thermodynamics.  Such  relations  have  been  developed 
by  Nernst,1  Mayer  and  Altmayer.2  and  others3  and 
expressed  in  terms  of  mathematical  formulas  from 
which  equilibrium  compositions  can  be  calculated: 
e.  g.,  the  Nernst  approximate  formula: 


log  K,   -  ,og 


=  —  ^-  +  i.7s(S»'  —  S»)   log 


By  the  use  of  such  formulas  the  ultimate  composi- 
tion representative  of  equilibrium  conditions  is  ob- 
tained. This  final  composition,  according  to  the  prin- 
ciples of  chemical  kinetics,  represents  the  end  point 
of  a  reaction  which  can  be  attained  only  through  a 
sufficient  lapse  of  time.  As  applied  to  the  production 
of  oil  gas,  a  progressive  decomposition,  in  which  time 
is  an  important  factor,  should  proceed  to  an  ultimate 
state  of  equilibrium. 

The  reactions  taking  place  in  the  decomposition  of 
petroleum  hydrocarbons  by  heat  are  numerous  and 
not  definitely  known.  In  the  industries  based  on 
these  decomposition  reactions,  as  in  the  making  of  oil 
gas,  carbureting  water  gas,  and  cracking  petroleum 
for  light  distillates,  the  chemical  nature  of  only  the 
initial  materials  and  the  final  products  are  determined, 
and  this  does  not  give  any  definite  knowledge  con- 
cerning the  intermediate  reactions.  The  breaking 
down  of  hydrocarbons  of  high  molecular  weights  to 
simpler  hydrocarbons  apparently  consists  in  numerous 
consecutive  and  concurrent  reactions,4  but  their  actual 
course  from  the  initial  material  to  the  final  products 
has  not  been  established.  Even  in  the  absence  of 

1  W.  Nernst,  "Theoretische  Chemie." 

3  Mayer  and  Altmayer,  Ber.,  40  (1907),  2134. 

2  H.  von  Wartenberg.  Z.  physik.  Chem.,  61  (1907),  366. 

4  Berthelot,    Ann.    chim.    phys.    (1866   to    1877);    Thorpe   and   Young, 
Liebig's  Ann.,  165  (1872),   1;   Proc.  Roy.  Soc.,  21  (1873),  184;  Norton  and 
Andrews,  Am.  Chem.  J  ,  8  (1886).  1;  Armstrong  and  Miller,  J.  Chem.  Soc., 
49  (1886),  74;  Lewes,  J.  Soc.  Chem.  Ind.,  11  (1892),  584;  Haber,  Bcr.,  29 
(1896),  2691;  J.  Gasbel..  34,  377,  435.  452;  Worstall  and  Burwell,  Am.  Chem 
J.,  19  (1897),  815;  Bone  and  Coward,  J.  Chem.  Soc.,  93  (1908),  1197;Hempel, 
J.  Gasbel.,  1910,  p.  53;  Kramer  and  Spilker,  Ber.,  33  (1910),  2265;  Lewes, 
Trans.  Chem.  Soc.,  69  (1892),  322;  Proc.  Roy.  Soc.,  55  (1894),  90;  57  (1905). 
394,  450;  Bone,  J.  Gasbel.,  51   (1908),  803;  Engler,  Ber.,  30  (1897),  2908. 

(3) 


such  knowledge,  the  theoretical  principles  of  chemical 
kinetics  which  apply  to  single  reactions  should  also 
hold  in  the  case  of  the  numerous  reactions  involved 
in  the  thermal  decompositions  of  petroleum  hydro- 
carbons. 

The  importance  of  the  variable  time  in  a  few  related 
decompositions  has  been  shown  by  a  number  of  in- 
vestigators. Lewes1  finds  that  the  decomposition 
of  ethylene  is  dependent  not  only  upon  temperature 
and  pressure  but  also  on  rate  of  flow.  Clement2  has 
shown  the  importance  of  the  time  factor  in  the  manu- 
facture of  producer  gas.  Hempel's3  experiments 
with  gas  oils  at  temperatures  between  700  and  900°  C. 
have  demonstrated  further  the  influence  of  the  rate 
of  oil  feed  upon  the  composition  of  the  products. 
J.  F.  Tocher4  has  also  shown  some  results  of  a  change 
in  the  rate  of  oil  feed.  A  technical  application  of  the 
time  factor  can  be  found  in  the  experiments  of  Jones.5 

In  varying  the  rate  of  oil  fed  into  a  retort  or  furnace 
for  the  production  of  oil  gas,  one  varies  the  time  during 
which  any  portion  is  heated  and  hence  the  time  al- 
lowed for  the  reaction.  With  a  very  slow  rate  of  oil 
feed,  the  reaction  would  attain  an  equilibrium  com- 
position representative  of  the  heating  zone  conditions. 
With  increasing  rates  of  oil  feed  the  time  allowed  for 
reaction  is  shortened  and  the  products  obtained  cor- 
respond to  an  earlier  stage  of  the  decomposition. 
The  composition  of  oil  gas  is  therefore  dependent  upon 
the  time  allowed  for  chemical  change.  Hence  the 
study  of  the  time  factor  in  the  making  of  oil  gas  should 
yield  interesting  and  practical  results. 

EXPERIMENTAL    CONSIDERATIONS 

A  study  of  the  reactions  of  gases  moving  through 
heated  vessels,  the  method  which  was  used  in  this 
investigation  and  is  representative  of  practice  in  oil 
gas  production,  involves  certain  features  of  design 
which  are  dependent  upon  the  theoretical  considerations 
of  reaction  velocity.  During  the  passage  of  any 
heating-zone-composition  through  the  cooling  zone, 
there  will  be  a  certain  change  in  composition  due  to  a 
reversal  of  reactions.6  The  extent  of  this  reversal 
will  depend  on  the  time  required  in  the  cooling  zone 

i  Lewes,  Proc.  Roy.  Soc.,  56  (1894),  90;  57,  594. 

-  Clement,  Bull.  30  (1909),  D.  of  111.  Eng.  Exp.  Sta. 

a  Hempel,  J.  Gasbel.,  1910,  pp.  53,  77,  101.  137  and  155. 

«  J.  F.  Tocher,  J.  Soc.  Chem.  Ind.,  13  (1894),  231. 

'  Jones.  Am.  Gaslight  J.,  99  (1913).  273. 

«  Nernst,  Z.  anorg.  Chem..  49  (1906).  213. 

(4) 


to  arrest  the  reactions.  Hence  the  more  quickly 
these  gases  are  cooled  after  leaving  the  heating  zone, 
the  more  nearly  will  the  product  obtained  be  repre- 
sentative of  the  heating  zone  conditions.  The  effi- 
ciency of  the  cooling  zone  in  arresting  the  reversal 
of  reactions  is  materially  increased  in  some  of  the  de- 
composition reactions  by  the  separation  of  carbon  in 
the  solid  phase,  making  it  possible  to  obtain  as  the 
product  a  gas  mixture  which  very  closely  approximates 
the  composition  of  the  mixture  in  the  heating  zone. 
It  is  thus  evident  that  reaction  velocity  is  important 
not  only  in  the  heating  zone,  but  also  in  the  cooling 
zone. 

Further  essential  considerations  in  the  attainment 
of  a  product  representative  of  heating  zone  conditions 
are  those  of  convection  and  diffusion.  As  shown  by 
Langmuir,1  diffusion  and  convection  act  in  a  way 
that  is  equivalent  to  decreasing  the  reaction  velocity. 
Convection  currents  may  be  set  up  by  differences  in 
temperatures  or  irregularities  in  design,  the  results 
of  which  will  tend  to  shorten  the  time  of  contact  for 
some  of  the  molecules  in  the  heating  zone.  The 
effect  of  diffusion  increases  with  temperature  as  the 
coefficient  of  diffusion  varies  approximately  with  the 
square  of  the  absolute  temperature.  Considering  the 
heating  zone  or  cooling  zone  separately,  raising  the 
temperature  increases  the  diffusion  effect  and  is  in  a 
sense  equivalent  to  shortening  the  time  of  contact. 
This  effect  may  be  a  material  consideration  in  the 
heating  zone  but  would  be  almost  negligible  in  the 
cooling  zone.  On  the  other  hand,  when  one  considers 
the  mutual  effect  of  the  two  zones,  diffusion  offers  an 
advantage,  due  to  the  differences  in  the  partial  pres- 
sures of  the  reacting  substances.  Differences  in  partial 
pressures  cause  those  substances  whose  proportions 
increase  with  rise  in  temperature  to  diffuse  from  the 
heating  zone  to  the  cooling  zone  and  vice  versa  those 
substances  whose  proportions  4  decrease  with  rise  in 
temperature  diffuse  in  the  opposite  direction.  .Hence, 
this  effect  aids  also  in  obtaining  products  more  nearly 
corresponding  to  the  heating-zone-composition. 

OIL    GAS    APPARATUS 

The  design  and  construction  of  an  apparatus  suitable 
for  carrying  out  the  study  of  the  behavior  of  hydro- 
carbon vapors  under  the  conditions  outlined  in  the 
foregoing  theoretical  discussion  involved  many  im- 

1  Langmuir,  J.  Am.  Chem.  Soc.,  30  (1908),  1742. 
(5) 


'Electrode  Holder 


£- • ' Cooling  Spray 

" Asbestos 

"A  sbestos  Disks 

'"Carbon  Resistor 


Window 

sl'.^^t--- -Carbon  side  Tube 
r*'*.V  "'i'""  C°rb°n  Jacket  Tube 
.-•Petroleum  Coke 


"-  Pyrometer  Sight 
Tube 


FIG.  I — RESISTANCE  FURNACE 
(6) 


portant  considerations.  In  such  an  apparatus  it  was 
desired  to  provide  for  working  with  constant  tempera- 
tures up  to  2300°  C.;  for  pressures  ranging  from  — 15 
Ibs.  to  100  Ibs.  gauge  per  sq.  in.;  for  constant  rates 
of  oil  feed  over  a  large  range;  for  suitable  means  of 
collecting  the  resultant  products;  and  for  numerous 
other  requirements. 

THE    FURNACE 

An  electrically  heated  carbon  tube  resistance  fur- 
nace, illustrated  in  Fig.  I,  was  constructed.  This 
furnace  embodies  the  use  of  a  carbon  tube  resistor 


•Insulating 
Cap 


•Insulation 
and  Packing 


Elecfric 
Lead  Connection 


Coofinq . 
Wafer 
Connection 


FIG.  II  —  ELECTRODE  HOLDER 


held  by  water-jacketed  electrode  holders  and  sur- 
rounded by  heat-insulating  material  enclosed  by  an 
iron  furnace  body  which  is  provided  with  suitable 
accessory  mechanisms  for  electrical  and  water-cooling 


connections,  feed  and  discharge  apparatus,  and  ob- 
servation of  temperatures  and  pressures. 

The  carbon  tube1  resistor  (A)  is  46  in.  long,  i  in. 
inside  diameter,  with  0.25  in.  wall.  Deducting  the 
electrode  holder  contact  length,  about  4  in.  at  each  end, 
this  gives  a  heating  zone  of  38.5  linear  inches  with 
120  sq.  in.  heating  surface  and  a  volume  equal  to 
30.5  cu.  in.  or  about  500  cc.  This  tube  is  copper  plated 
externally  at  each  end  to  give  a  suitable  contact  sur- 
face of  1 8  sq.  in.  with  each  electrode  holder. 

The  electrode  holders  (BB)  are  integral  bronze 
castings  with  cored  water  jackets  and  with  flanges  for 
bolting  to  the  furnace  heads.'  The  construction  is 
shown  in  some  detail  in  Fig.  II.  Into  the  main  body 
of  the  holder  outside  of  the  flanges,  are  drilled  and 
tapped  the  water-jacket  connections  'and  binding 
posts  for  the  electric  leads.  The  outside  ends  are 
further  provided  with  carefully  insulated  stuffing  boxes 
and  caps  in  order  to  separate  the  heating  element, 
electrically,  from  the  feed  and  discharge  mechanisms 
of  the  assembled  apparatus.  The  flanges,  bolts,  and 
nuts  are  insulated  with  sheet  mica  to  isolate  the  heating 
element  from  the  furnace  casing. 

The  resistor  tube  is  surrounded  by  a  large  concentric 
carbon  tube  (C),  3  in.  inside  diameter  and  0.50  in.  wall, 
which  is  insulated  from  the  electrode  holders  by  as- 
bestos disks.  This  construction  leaves  an  annular 
dead  gas  space  of  0.75  in.  around  the  resistor.  Be- 
tween this  large  carbon  tube  and  the  furnace  casing 
powdered  petroleum  coke  is  packed  for  heat  insulation. 

The  furnace  body  (D)  is  made  from  extra  heavy 
wrought  iron  pipe  with  screwed  and  peened  flanges 
at  each  end.  To  these  are  bolted  blank  companion 
flanges  centrally  bored  to  receive  the  bodies  of  the 
electrode  holders  and  faced  to  seat  the  flanges.  The 
electrode  holders  are  each  held  in  position  by  six 
0.5  in.  stud  bolts  drilled  and  tapped  into  the  furnace 
heads.  As  above  stated  the  mountings  of  the  elec- 
trode holders  are  mica-insulated  from  any  contact 
points  with  the  furnace  casing.  Three  solid  bosses, 
3  in.  diameter  by  0.5  in.  thick,  are  autogenously 
welded  on  the  outside  walls  of  the  furnace  casing  and 
are  drilled  and  tapped  for  i  in.  brass  extensions  which 
serve  as  sight  tubes  (EE'E"). 

These  extension  tubes  register  with  and  support 
carbon  side  tubes  (FF'F"),  0.75  in.  inside  diameter 
and  0.125  in.  wall,  which  connect  the  sight  tubes  with 

1  Carbon  tubes  were  obtained  from  the  National  Carbon  Co. 
(8) 


the  annular  space  around  the  resistor.  The  outer  ends 
of  the  sight  tubes  are  provided  with  glass  windows 
0.25  in.  thick.  This  combination  gives  a  straight  way 
view  into  the  resistor  chamber  at  three  points  along 
its  length. 

The  water-cooling  system  for  the  furnace  casing 
consists  of  a  perforated  yoke  of  water  pipe  (G)  at  the 
top  for  spray  cooling  and  an  annular  catch  basin  (H) 
at  the  bottom. 


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1100 


900 


700 


500 


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POWER.  KILO  WATTS 
FIG.  Ill — POWER  CONSUMPTION  CURVE  FOR  RESISTANCE  FURNACE 

OPERATION    AND    TEST    OF    FURNACE 

The  power  required  to  heat  the  furnace  is  derived 
from  a  single  phase,  60  cycle,  50  kw.  alternating  cur- 
rent generator,  having  a  range  of  5  to  100  volts  which 
can  be  regulated  within  narrow  limits  by  a  switchboard 
and  rheostat  combination.  Thus  the  temperature 
of  the  furnace  can  be  readily  controlled.  Power  was 
measured  by  the  use  of  a  portable  Weston  ammeter, 

(9) 


voltmeter,  and  wattmeter  placed  in  close  proximity 
to  the  furnace.  The  readings  from  these  three  in- 
struments made  it  possible  for  the  operator  to  determine 
the  power  consumption  of  the  furnace  and  to  check 
the  proper  working  of  the  apparatus. 

Ordinarily  it  required  about  an  hour  to  heat  the 
furnace  to  a  constant  temperature  after  the  power  had 
been  turned  on.  The  high  temperatures  are  measured 
by  sighting  through  the  observation  tube  windows 
with  a  Wanner  optical  pyrometer;  no  temperature 
corrections  are  necessary.  The  low  temperatures  are 
measured  by  replacing  the 
glass  windows  by  small 
stuffing  boxes  through 
which  pyrods  are  inserted. 
The  power  used  for  the 
various  temperatures  is 
shown  in  Fig.  III.  This 
furnace  has  been  tested  at 
various  temperatures  rang- 
ing from  500  to  2300°  C. 
and  held  constant  at  such 
temperatures  for  several 
hours  at  a  time.  In  these 
tests  the  readings  at  the 
three  different  observation 
points  agreed.  In  one  of 
the  tests  the  furnace  was 
held  at  1600°  C.  for  four 
hours  without  requiring  any 
regulation  of  the  power. 
A  hydrostatic  pressure  test 
to  200  Ibs.  per  sq.  in.  was 
made  on  the  assembled 
furnace  with  the  feed  and 
discharge  mechanisms  at- 
tached. 

The  carbon  resistor  is 
the  only  part  of  the  furnace  which  requires  renewal. 
Yet  a  single  tube  has  been  used  for  fifty  runs  at 
various  temperatures.  Whenever  it  is  necessary  to 
renew  the  resistor,  the  electrode  holders  are  removed 
and  a  new  tube  fitted. 

PREVAPORIZER 

The  object  of  the  prevaporizer  is  to  vaporize  the  oil 
before  it  enters  the  heating  zone  of  the  furnace. 

The  prevaporizer,  Fig.  IV,  consists  in  a  3/s  in.  brass 

do) 


I 


•Asbestos 


-Nichrome 
Wire  Heating 
Elements 


Asbestos 
pacH'mg  around 
Pipe 


••Iron  Wire  Filling 


FIG.  IV — PREVAPORIZER 


pipe  1 8  in.  long,  containing  a  bundle  of  iron  wire  for 
spreading  the  oil.  It  is  electrically  heated  from  the 
outside  by  8  turns  to  the  inch  of  No.  18  B.  &  S.  nichrome 
resistance  wire  properly  insulated  from  the  tube  by 
four  wrappings  of  asbestos  paper.  For  heat  conserva- 
tion the  whole  is  surrounded  by  standard  85  per  cent 


To  Oil  supply 
Tank. 


L-  To  Pressure 
Gauge 


To  Oil  supply  Tank 


bJ 
FIG.  V — STATIC  HEAD  AND  FEED  REGULATOR 

magnesia  pipe  covering.  The  power  required  for 
heating  the  prevaporizer  is  furnished  from  a  separate 
direct  current  line  and  regulated  by  the  use  of  a  lamp 
bank. 

Prevaporization  was  found  to  be  an  essential  feature 
as   experiments  showed   that   even   when   the   heating 

(n) 


zone  temperature  of  the  furnace  was  1400°  C.  and 
the  rate  of  oil  feed  50  drops  per  minute,  the  oil  dropped 
directly  through  the  heated  carbon  tube  and  came  out 
at  an  equal  rate  with  very  little  vaporization;  this  result 
was  apparently  due  to  spheroidal  effect  and  lack  of 
contact  with  the  heated  surface.  With  a  solid  or  vapor 
passing  through  the  tube  under  the  same  conditions, 
the  solid  would  become  heated  by  radiation  and  the 
vapor  mainly  by  conduction.  Prevaporization  was 
found  to  be  incomplete  at  very  high  rates  of  oil  feed, 
i.  e.,  the  prevaporizer  has  a  maximum  capacity."  As  an 
additional  precaution,  at  high  feed  rates,  the  wire 
filling  of  the  prevaporizer  was  extended  into  the 
heating  zone  of  the  furnace. 

STATIC    HEAD    AND    FEED    REGULATOR 

The  object  of  the  static  head  and  feed  regulator  is 
to  provide  for  an  accurate  and  steady  rate  of  oil  feed 
which  in  turn  controls  the  time  factor. 

The  static  head  regulator,  shown  in  Fig.  V.  is  made 
up  of  a  specially  designed  cast  brass  casing.  A,  with  a 
gauge  glass,  B,  and  a  screw  cap,  C,  which  may  be 
removed  for  internal  adjustment.  The  inside  mech- 
anism consists  of  a  cork  float,  D,  which  operates  a 
needle  valve,  E.  This  constant  level  regulator  is 
also  connected  with  the  oil  supply  tank,  the  feed  mech- 
anism, the  pressure  equalizer  pipe,  and  the  pressure 
gauge.  Valve  F  is  a  stop-valve  to  be  closed  when  the 
apparatus  is  not  in  use. 

The  sight  feed  regulator  H  is  constructed  from  a 
brass  casting  provided  with  two  glass  windows,  II', 
and  an  angle  needle  valve,  J,  to  regulate  the  rate  of 
oil  feed.  Connections  are  made  from  this  with  the 
static  head  regulator,  prevaporizer,  and  pressure 
equalizer  and  admixture  pipes  as  shown  in  Fig.  V. 

A  constant  head  of  oil  is  necessary  in  order  that  a 
fixed  opening  of  the  feed  valve  J  may  give  a  definite 
and  uniform  rate  of  oil  feed.  This  is  accomplished 
by  the  cork  float  D  operating  the  needle  valve  E, 
which  admits  oil  from  the  storage  tank  at  a  rate  equal 
to  the  rate  of  feed.  In  order  to  insure  the  proper 
working  of  this  mechanism,  a  gauge  glass,  B,  is  pro- 
vided, which  .registers  the  oil  level.  This  level  has 
been  found  to  vary  not  more  than  1/8  in.  regardless 
of  the  level  in  the  oil  supply  tank.  The  oil  feed  is 
regulated  to  the  desired  rate  by  adjusting  the  needle 
valve  J,  according  to  observations  made  through  the 
windows  I. 

(12) 


Table  I  contains  data  taken  from  some  of  the  ex- 
perimental runs  and  serves  to  show  the  range  of  ac- 
curacy of  oil  feed  obtained  by  this  mechanism: 

TABLE  I — RANGE  OP  ACCURACY  OF  OIL  FEED 

Test                 Rate  of  feed  per  minute  Period  of  test            Variation 

1 8  drops  3  hrs.  None 

2 100  drops  2  hrs.  1  drop 

3 5.4cc.  1  hr.  None 

4 15.8cc.  30  min.  0.5  cc. 

5 69.0cc.  8  min.  None 

The  pressure  of  the  whole  system  is  equalized  by  a 
pressure  equalizing  pipe,  G,  which  communicates  the 
furnace  pressure  through  the  sight  feed  to  the  static 
head  regulator  and  the  oil  supply  tank. 

Pipe  K  is  used  for  recirculating  the  gases  made  or 
for  admixing  other  material  with  the  oil. 

OIL    SUPPLY    TANK 

The  oil  supply  tank  (see  Fig.  VI),  with  a  capacity 
of  600  cc.,  is  made  from  standard  1.5  in.  brass  pipe 
and  fittings.  To  this  a  gauge  glass  is  connected  and 
provided  with  a  parallel  meter  stick  carrying  a  sliding 
pointer.  This  arrangement  is  calibrated  for  volume 
and  enables  the  operator  to  verify  the  uniformity  of 
the  rate  of  oil  flow  and  hence  the  accuracy  of  the  con- 
stant head  apparatus. 

GAS    HOLDERS 

The  gas  holders  are  balanced  bell  holders  with  water 
seal.  These  are  calibrated  and  provided  with  a  meter 
stick  and  pointer  in  order  to  facilitate  the  recording  of 
the  rate  of  gas  generation  during  a  run. 

FEED    AND    DISCHARGE    MECHANISM 

Both  the  oil  feed  mechanism  and  the  condensing 
system  are  carried  on  the  supporting  framework  by 
swinging  arms.  The  connections  to  the  furnace  at 
their  respective  ends  are  made  through  ground  joint 
unions.  When  cleaning,  renewals  or  repairs  to  the 
furnace  are  necessary,  the  unions  may  be  disconnected 
and  the  mechanism  swung  aside  without  disturbing 
the  furnace. 

ASSEMBLY    AND    OPERATION 

The  arrangement  of  the  complete  apparatus  ready 
for  operation  is  shown  in  Fig.  VI.  At  the  beginning 
of  an  experiment  the  oil  tank  is  first  filled  with  oil; 
after  the  feed  valve  has  been  adjusted  to  the  desired 
rate  of  oil  feed,  oil-tank  readings  are  taken  at  definite 
intervals  of  time.  ' 

The  oil  passes  from  the  supply  tank  to  the  static 

(13) 


FIG.  VI — Oil,  GAS  APPARATUS 


(14) 


TABLE  II — RECORDS  OF  RUNS  AT  DIFFERENT  RATES  OF  OIL  FEED 
SLOW  RATE  OF  OIL  FEED 


Time 
11.15 
11.20 
11.25 
11.30 
11.35 
11.40 
11.45 
11.50 
11.55 
12.00 
12.05 


Temp. 
K.  W.         °  C. 

Gauge  pressure 
Lbs.  per  sq.  in. 

Oil  rate               Gas  rate 
Cc.  per  min      Liters  per  min. 

4  0            1010 

0 

2.1 

0 

2.1                     2.0 

1666 

0 

2.0 

.9 

.... 

0 

2.0 

.7 

0 

2.1                     1 

.8 

1666 

0 

2.2 

.8 

.... 

0 

2.0 

.9 

4  i 

0 

2.1 

.8 

.    .             1010 

0 

2.2 

.8 

0 

2.1 

.8 

!  !        1666 

1 

2.1 

.7 

50  min.  105  cc.  92  liters 

PERCENTAGE    GAS  ANALYSIS  —  SLOW    RATE    OF    FEED  —  MARCH    8,    1915 

CO*       111.      02  CO       H2     CwH2M+2  N2  (diff->  Total  Carbon      Tar 

0.8  1.0     54.5          29.0  7.4          100       Little       Trace 

...  ...      60.5         32.0  ...          100        ........... 


0.6 


or 


6.7 
7.5 


MODERATE  RATE  OF  OIL  FEED 


Gauge  pressure 

Oil  rate 

Gas  rate 

Time 

Temp.,  °  C. 

Lbs.  per  sq.  in. 

Cc.  per  min. 

Liters  per  min. 

4.10 

1000 

0 

14.0 

4.12 

'    °  ' 

0 

13.5 

5.8 

4.14 

0 

13.5 

5.8 

4.15 

0 

13.0 

6.2 

4.20 

0 

13.5 

6.5 

4.25 

'.    '.  '. 

0 

13.5 

5.3 

4.30 

0 

13.5 

6.3 

4.35 

1666 

0 

13.0 

6.5 

25  min.  240  cc.  160  liters 

PERCENTAGE  GAS  ANALYSIS — MODERATE  RATE  OF  FEED — APRIL  16,  1915 

C02      111.       02       CO       H2     CMH2w+2     N2  (diff.)    Total  Carbon    Tar 

01      19  2     0.0     0.8     44.3       35.2                0.4           100      Little    125  cc. 
or...      19.5      44.8       35.7  ...  100        

RAPID  RATE  OF  OIL  FEED 


Time 

Temp 
C. 

Gauge  pressure         Oil  rate                Gas  rate 
Lbs.  per  sq.  in.     Cc.  per  min.       Liters  per  min. 

3.30 
3.32 
3.36 
3.38 
3.41 

1000 

1666 

0 
0 
0 
0 
0 

44.0 
44.5 
44.5 
45.0 
44.5 

13.0 
13.2 
13.3 
13.3 

1  1  min. 

490  cc. 

445  liters 

PERCENTAGE 

GAS 

ANALYSIS  —  RAPID    RATE 

OF  FEED  —  APRIL   16,    1915 

C02      111. 

02 

'CO       H2 

CMH2n+2  N2  (diff.)   Total 

Carbon   Tar 

0.0     35.0 

or                37.7 

0.6 

1.8     21.8 
23.5 

36.0 
38.8 

4.8            100 

Trace  245  cc. 

head  regulator  and  out  through  the  feed  adjusting 
valve  to  the  prevaporizer.  From  here  the  vaporized 
oil  is  carried  directly  into  the  heating  zone  of  the 
furnace. 

The  oil  gas  runs  were  made  over  a  range  of  constant 
temperatures  from  800°  to  1600°  C. 

Temperature  observations,  during  a  run,  showed 
that  the  feed  end  of  the  resistor  was  50°  to  100°  C. 
cooler  than  the  center  and  discharge  points  which  re- 
mained practically  the  same.  This  lower  temperature 
of  the  feed  end  of  the  reaction  chamber  is  obviously 
due  both  to  the  heating  up  of  the  oil  vapors  and  to  the 
large  amount  of  heat  required  for  the  endothermic 
reactions  taking  place  in  this  part  of  the  tube.  Further- 

(15) 


more,  the  deposition  of  carbon  here  may  reduce  the 
resistance  and  hence  lower  the  temperature. 

The  measurement  of  the  high  temperatures  by  the 
optical  pyrometer  offered  no  difficulties  as  there  were 
no  fumes  present  in  the  furnace. 

The  hot  gases  are  discharged  from  the  reaction 
chamber  directly  into  the  primary  condenser  where 
the  reactions  are  arrested  by  the  cooling.  From  here 
the  gases  go  through  the  tar  drip  which  is  followed 
by  a  secondary  condenser  and  thence  out  to  the  gas 
holders,  where  the  rate  of  gas  generation  is  noted  at 
definite  intervals  of  time.  The  condensates  from  both 
the  primary  and  secondary  condensers  run  into  the 
same  tar  drip  from  which  they  may  be  readily  removed 
at  the  end  of  each  experiment. 

Typical  records  of  runs  are  shown  in  Table  II. 

GAS    SAMPLING    AND    ANALYSIS 

The  gas  from  the  runs  was  collected  in  the  balanced 
bell  gas  holders  already  described.  Care  was  always 
taken  to  saturate  the  seal  water  with  a  similar  gas 
previous  to  the  collection  of  the  run  from  each  ex- 
periment. Before  taking  a  sample  of  gas  from  the 
holders  for  analysis,  the  product  was  allowed  to  stand 
a  sufficient  length  of  time  for  complete  mixing  by 
diffusion  and  for  the  settling  out  of  any  tar  or  carbon 
that  might  have  been  carried  over. 

The  gas  samples  were  analyzed  by  the  standard 
methods1  with  a  few  modifications  to  meet  special 
requirements.  The  Hempel  equipment  was  used  in 
all  analyses  and  the  order  of  procedure  was  as  fol- 
lows : 

i — Absorption  of  the  carbon  dioxide  with  KOH  solution. 

2 — Absorption  of  the  illuminants  with  fuming  sulfuric  acid 
(23  per  cent  free  SO3). 

3 — Absorption  of  the  oxygen  by  alkaline  pyrogallol. 

4 — Absorption  of  the  carbon  monoxide  by  two  ammoniacal 
cuprous  chloride  solutions. 

5 — Partial  combustion  of  the  hydrogen  by  passing  20  to  30  cc. 
of  the  remaining  gas  mixed  with  the  proper  proportion  of  pure 
oxygen  over  palladium  black  heated  to  70°  to  80°  C. 

6 — Explosion  of  the  remaining  hydrocarbon-oxygen  mixture. 

The  partial  combustion  of  hydrogen  in  gas  mixtures 
containing  percentages  above  90  per  cent  was  difficult 
on  account  of  the  danger  of  explosion.  In  such  cases 
the  mixture  was  exploded  directly  and  calculated 
as  hydrogen  and  methane  from  the  formulas, 

1  Dennis,  "Gas  Analysis."  1913. 

(16) 


cc.  of  H2  =        1--  -  and   cc.  of  CH4  =  C02, 

3 

where  T.  C.  =  total  contraction  noted  directly  after 
the  explosion  and  CO2  =  contraction  due  to  absorption 
with  KOH  after  explosion. 

In  the  partial  combustion  of  hydrogen  followed  by 
the  explosion  of  the  residual  gas  mixture,  it  was  often 
difficult  to  obtain  an  explosion  by  using  air  as  the 
source  of  oxygen.  This  difficulty  was  avoided,  how- 
ever, by  the  use  of  pure  oxygen  in  such  an  amount 
that,  after  the  removal  of  the  hydrogen  by  the  pal- 
ladium black  treatment,  an  explosive  mixture  re- 
mained. 

From  the  total  contraction  and  the  carbon  dioxide 
found  by  explosion,  the  volume  of  saturated  hydro- 
carbons was  calculated  by  the  following  formula:1 

2T.C.  —  CQ2 


This  gave  the  total  volume  of  all  the  saturated 
hydrocarbons:  methane,  ethane,  propane,  etc.  From 
the  V  and  the  CO2  a  mean  value  of  n  for  the  type 
formula  CMH2n+2  was  obtained,  which  gave  an 
indication  of  the  nature  of  the  hydrocarbons  present, 

C02 

that  is,  n  =    —   . 

There  is  no  proof  that  the  saturated  hydrocarbons 
do  not  contain  hydrocarbons  of  higher  molecular 
weight  than  ethane.  The  true  percentages  of  each 
of  the  CnH2w+2  hydrocarbons  can  be  determined  only 
by  the  fractional  distillation  methods  of  Burrell2  and 
his  associates,  of  the  U.  S.  Bureau  of  Mines. 

In  common  analytical  practice,  when  the  hydrogen 
is  separated  by  partial  combustion,  the  remaining  gas 
is  assumed  to  contain  only  methane  and  ethane  and  is 
calculated  as  such.  This  obviously  would  give  an 
error  dependent  upon  the  amount  of  heavier  hydro- 
carbons present. 

For  the  calculation  of  the  respective  volumes  of 
ethane  and  methane  present  on  the  above  assumption, 
the  following  formulas  were  used: 

4CO2  —  2  T.  C. 

cc.  of  C2H6  =    •  ~~  and 

3 

cc.  of  CH4  =  C02  —  2  C2H6. 

1  DeVolderc  and  DeSmet.  Z.  anal.  Chem.,  49  (1910),  661. 
*  Burrell  and  Seibert,   J.   Am.   Chem.   Soc.,   36   {1914),    1537;   Burrell 
and  Robertson,    J.  I.  E.  C.,   1  (1915),  17,  210. 

(17) 


THE    TIME    FACTOR 

The  experimental  values  found  in  this  investigation 
are  considered  on  the  assumption  that  the  true  time 
factor  is  a  function  of  the  rate  of  oil  feed.  As  stated 
above,  the  true  time  factor,  which  represents  the  in- 
terval of  time  in  which  the  reactions  progress,  is  de- 
pendent upon  the  theoretical  considerations  of  reac- 
tion velocity.  It  is  substantially  a  function  indirectly 
proportional  to  the  rates  of  oil  feed;  i.  e.,  an  increase 
in  the  rate  of  oil  feed  decreases  the  time  of  reaction. 

On  the  other  hand,  the  rate  of  gas  production  might 
be  considered  as  a  means  of  obtaining  a  better  ap- 
proximation of  the  true  time  factor.  This  would 
necessitate  the  calculation  of  the  volumes  of  the 
gases  to  the  reaction  zone  conditions.  Furthermore, 
tars  would  have  to  be  considered,  in  case  of  their 
formation.  Such  a  method,  even  if  both  tars  and  gases 
were  considered,  would  not  give  a  value  approximating 
the  true  time  factor,  as  the  original  oil  vapors  occupy 
a  much  smaller  volume  than  their  decomposition 
products;  in  fact  decomposition  in  the  reaction  zone 
proceeds  with  a  continuous  increase  in  volume.  It  is 
apparent  then  that  this  basis  of  a  time  factor  would  be 
impractical  either  for  experimental  study  or  for  tech- 
nical purposes.  For  these  reasons  the  time  factor  as 
based  on  the  rate  of  oil  feed  was  selected  for  this  in- 
vestigation as  it  offers  a  comparative  value  for  theo- 
retical considerations  and  is  an  easily  measured  quantity, 
as  well  as  a  readily  controllable  variable  for  practical 
work. 

EXPERIMENTAL 

A  water-white  kerosene,  boiling  between  150^290°  C., 
was  used  in  all  experimental  runs. 

All  runs  were  made  at  atmospheric  pressure,  any 
variation  of  which  was  indicated  by  the  pressure  gauge. 

The  complete  gas  analyses  always  showed  varying 
percentages  of  carbon  dioxide,  carbon  monoxide,  and 
air  (e.  g.,  see  Analyses  in  Table  II),  so  that  the 
figures  for  illuminants,  hydrogen,  and  saturated 
hydrocarbons  did  not  present  these  constituents  in 
their  proper  relationships.  This  difficulty  was  over- 
come by  recalculating  the  analyses  to  the  illuminant- 
hydrogen-saturated  hydrocarbon  basis  (see  Analyses 
in  Table  II)  and  all  subsequent  data  are  presented 
from  this  view  point. 

EFFECT    OF    RECIRCULATION    OF    GASEOUS    PRODUCTS 

In  this  investigation  it  was  necessary  first  to  prove 
(18) 


that  in  the  production  of  oil  gas,  chemical  equilibria 
are  not  obtained,  for  if  such  were  not  the  case,  a  study 
of  the  time  factor  would  be  valueless.  This  point  was 
proved  by  runs  at  slow  rates  of  oil  feed,  so  as  to  allow 
a  considerable  time  for  reaction,  and  subsequent 
recirculations  of  the  products.  Slow  rates  of  oil  feed 
were  selected  because,  if  equilibria  were  not  established 
at  such  rates,  it  is  self-evident  that  they  would  not  be 
established  at  higher  rates  with  correspondingly  less 
time  for  reaction. 

In  experimental  data  given  in  Table  III  three 
different  rates  of  oil  feed  at  the  same  temperature, 
1200°  C.,  were  selected  and  the  recirculations  (a  and  b) 
made  at  rates  equal  to  their  respective  rates  of  gas 

TABLE  III — GAS  GENERATION  AND  RECIRCULATION  AT  1200°  C. 
Run         Oil  rate  Gas  rate  GAS  ANALYSES  (PERCENTAGES) 

No.    Cc.  per  min.   Liters  per  min.  Ilium.  Hz  Cn~H.2n-}-2 

1  1.1  1.25  0.0  92.5  7.5 

la  ...  1.25  0.0  94.0  6.0 

2.4  2.4  1.1  90.5  8.4 

2a  2.4  0.0  92.8  7.2 

2b  ...  2.4  0.0  93.2  6.8 

3  6.0  5.3  1.5  88.2  10.3 

3a  5.3  0.5  88.9  10.1 

36  ...  5.3  0.0  90.5  9.5 

generation.  Rates  that  gave  practically  no  tar  were 
selected;  this  was  necessary  because  tars,  if  present, 
undoubtedly  take  part  in  the  reactions  in  the  heating 
zone. 

A  consideration  of  the  general  velocity  equation  in 
conjunction  with  the  above  data  will  show  some 
interesting  relations  between  reaction  velocity  and 
gas  recirculation. 

— 
dt 

\ 

Here  the  rate  of  change  is  dependent  upon  the 
respective  velocity  constants  of  the  reverse  reactions 
and  the  concentrations  of  the  reacting  substances. 
For  any  one  temperature  the  velocity  constants  have 
a  fixed  value.  Should  the  decomposition  reactions 
have  completed  themselves  or  come  to  equilibrium, 
dx/dt  would  have  been  equal  to  zero,  but  the  above  data 
shows  that  this  was  not  the  case,  and  hence  equilibrium 
was  not  attained.  As  the  reactions  approach  equi- 
librium, the  respective  velocities  of  the  two  reverse 
reactions  become  more  nearly  equal,  i.  e.y  the  rate  of 
change,  dx/dt,  is  a  decreasing  function  as  equilibrium 
is  approached.  The  results  in  Table  III  show  this 

(19) 


effect  quite  conclusively,  as  the  change  in  the  second 
recirculation  is  less  than  that  in  the  first. 

In  case  one  considers  the  reactions  to  proceed  to 
completion  in  one  direction  only,  the  same  theoretical 
conclusions  hold. 

In  the  above  gas  mixtures,  with  no  illuminants 
present,  the  saturated  hydrocarbon  percentages  were 
found  to  consist  entirely  of  methane.  The  reaction 
involved  at  such  a  stage  of  the  decomposition  consists 
only  in  the  decomposition  of  methane  into  carbon  and 
hydrogen.  The  equilibrium  composition  "of  this  re- 
action at  1200°  C.  (calculated  according  to  the  formulas 
of  Nernst  or  Mayer  and  Altmayer)  should  show  not 
more  than  0.3  per  cent  methane,  as  has  been  experi- 
mentally proved  by  many  investigators.1  The  reason 
that  this  value  was  not  obtained  in  the  above  ex- 
periments is  that  sufficient  time  was  not  allowed  for 
the  reactions  to  reach  equilibrium.  The  intervals 
of  reaction  time  in  the  runs  in  Table  III  calculated 
from  the  gas  rates,  temperature,  pressure  and  volume 
of  heating  zone,  amounted  to  only  a  few  seconds— 
5,  2l/2  and  i  second,  respectively — for  Nos.  i,  2  and  3. 
Equilibrium  compositions  could  be  attained  only  by 
the  lapse  of  many  minutes  in  the  heating  zone.  This 
emphasizes  the  fact  that  equilibrium  compositions  are 
not  obtained  in  oil  gas  practice  and  further  that  it 
would  be  impractical  to  run  an  oil  gas  generator  at 
such  rates  of  oil  feed  as  would  even  approximate 
equilibrium  compositions. 

CHANGE    OF    COMPOSITION    WITH    RATE    OF    OIL    FEED    AT 
CONSTANT    TEMPERATURE 

The  changes  of  composition  with  the  rate  of  oil  feed 
at  constant  temperature  are  plotted  from  the  experi- 
mentally determined  data  in  Fig.  VII.  In  general, 
these  curves  show  that  a  decrease  in  the  oil  rate,  *.  e,, 
an  increase  in  the  time  of  reaction,  at  any  one  constant 
temperature,  results  in  a  greater  degree  of  decomposi- 
tion. 

For  any  two  temperatures  that  can  be  compared 
with  reference  to  percentage  of  any  one  selected  con- 
stituent, the  higher  temperature  will  result  in  an 
equivalent  degree  of  the  decomposition  at  a  much  higher 
rate  of  oil  feed.  However,  the  total  compositions  of 
the  gases  produced  at  the  different  temperatures  are 

i  Bone  and  Jerdan,  J.  Chem.  Soc.,  71  (1897).  41;  79  (1901),  1042; 
Mayer  and  Altmayer,  Ber.,  40  (1907),  2134;  H.  von  Wartenberg,  Z.  physik. 
Chem.,  61  (1907),  366;  Bone  and  Coward,  J.  Chem.  Soc.,  93  (1908),  1197. 
93  (1908),  1975;  Pring,  J.  Chem.  Soc..  97  (1910).  498;  Pring  and  Fairlie, 
Ibid.,  99  (1911).  1796;  101  (1912),  91;  also  J.  I.  E.  C.,  4  (1912),  812 

(20) 


not  strictly  comparable,  i.  e.,  the  percentages  of  il- 
luminants  or  saturated  hydrocarbons  for  equal  per- 
centages of  hydrogen  are  not  the  same.  This  is  ap- 
parently due  to  different  reactions  taking  place  at  the 
different  temperatures  and  to  the  unequal  effect  of  the 
different  temperatures  on  the  velocities  of  the  various 
reactions. 

It  will  be  noted  that  at  low  temperatures  and  at 
high  rates  of  oil  feed  a  decrease  or  increase  in  the  oil 
rate  has  comparatively  little  effect  on  the  percentages 
of  hydrogen  or  illuminants  in  the  gaseous  products. 
This  suggests  that  there  must  be  a  minimum  per- 
centage of  each  constituent  at  these  temperatures. 
Yet  one  must  not  conclude  from  these  facts  that  the 
decompositions  at  the  low  temperatures  proceed  in 
abrupt  stages,  as  this  phenomenon  finds  explanation 
in  a  more  close  consideration  of  the  true  time  factor. 
From  Fig.  IX  it  will  be  seen  that  the  rates  of  gas  gen- 
eration do  not  undergo  material  change  over  a  con- 
siderable range  of  oil  feed.  On  the  assumption  that 
the  volumes  of  the  tars  in  the  heating  zone  are  ap- 
proximately equal,  then  the  reaction  periods  for  the 
high  rates  of  oil  feed  are  almost  the  same  and  should 
give  gaseous  products  of  similar  compositions. 

In  accordance  with  the  theoretical  considerations, 
the  maximum  decomposition  at  any  one  temperature 
can  be  attained  only  at  equilibrium,  which  is  char- 
acteristic of  an  extremely  long  time  for  reaction. 
The  curves  in  Fig.  VII  point  toward  such  equilibrium 
compositions  at  the  slow  rates  of  oil  feed.  Such  com- 
positions can  in  all  probability  be  attained  in  the 
heating  zone  at  extremely  slow  rates  of  oil  feed  but 
experimental  results  would  not  verify  this  on  account 
of  the  reversal  of  reactions  which  would  take  place 
in  the  cooling  zone. 

CHANGE    OF    COMPOSITION    WITH   TEMPERATURE    AT    CON- 
STANT   RATES    OF    OIL    FEED 

In  general,  the  constant  feed  curves1  in  Fig.  VIII 
show  that  increase  in  temperature  results  in  a  greater 
degree  of  decomposition  and  that  there  are  definite 
temperatures  at  which  maximum  and  minimum  per- 
centages of  the  various  constituents  of  the  gas  mixtures 
exist.  The  maxima  for  hydrogen  and  the  minima  for 
saturated  hydrocarbons  indicate  to  a  complete  decompo- 
sition of  the  oil  into  carbon  and  hydrogen.  The 

1  Plotted   from   values   obtained   by   interpolation   from   the   curves  in 
Fig.  VII. 

(21) 


100 
90 
80 

z:70 

UJ 

8 
geo 

i50 

cc.    . 
£40 


ri    FT7 

CQNSTANT  TEMPERATURE- 
CURVES.  HYDROGEM 


K 


\ 


30 


20 


fib 


10          20         30         40         50          60        70         80         90 
RATE  OFOILFEED-cc.permin. 


COMSTAMT  TEMPERATURE  CURVES 
SATURATED  HYDROCARBONS F 


20         30         40          50  '      60         70         80  -      9C 
RATE  OFOIL  FEED -cc.  permin. 


10          20          30         40          50         60         70         80          90 
RATE  OF  OIL  FEED-  cc.  per  mm. 

FIG.  VII — CONSTANT  TEMPERATURE  CURVES 


(22) 


1000  1200 

TEMPERATURE.  DEG.C. 


1400 


1600 


1000  1200 

TEMPERATURE.DEG.C. 


1400 


1600 


800 


1000  1200  1400 

TEMPERATURE.DEG.C. 

FIG.  VIII — CONSTANT  FEED  CURVES 
(23) 


i600 


minima  for  illuminants  exist  at  a  lower  temperature 
than  the  minima  for  saturated  hydrocarbons  at  the 
same  rates  of  oil  feed,  i.  e.,  in  the  complete  thermal 
decomposition  of  hydrocarbon  oils  into  carbon  and 
hydrogen,  the  illuminants  disappear  before  the  satu- 
rated hydrocarbons.  The  curves  for  hydrogen  and 
for  illuminants  seem  to  indicate  minima  and  maxima, 
respectively,  as  shown  by  the  extrapolations.  On 
the  other  hand,  the  percentages  of  saturated  hydro- 
carbons show  true  maxima  dependent  upon  the  rate 
of  oil  feed  and  the  temperature. 

PRODUCTION    OF    HYDROGEN 

Table  IV  shows  that  at  1600°  C.,  with  increasing 
rates  of  oil  feed,  the  percentages  of  hydrocarbons  in 
the  resulting  gases  decrease  until  a  maximum  of  de- 

TABLE  IV — PRODUCTION  OF  HYDROGEN  AT  1600°  C. 
Run      Oil  rate  Gas  rate  GAS  ANALYSES  (PERCENTAGES) 

No     Cc.  per  min.     Liters  per  min.  Ilium.  Hz  ^-n^2n  +  2 

1  69.0  54.0  11.8  73.1  15.1 

2  32.4  34.0  1.6  96.0  2.4 

3  11.5  13.0  0.0  99.2  0.8 

4  6.8  8.3  0.0  100.0  0.0 

5  2.4  2.9  0.0  100.0  0.0 

6  0.27  ....  0.2  98.6  1.2 

7  0.15                      0.7  96.8  2.5 

composition  is  reached,  when  the  oil  is  completely 
decomposed  into  carbon  and  hydrogen.  » 

As  stated  above,  under  the  recirculation  of  gas, 
even  at  1200°  C.  the  hydrocarbons  should  be  com- 
pletely decomposed  into  carbon  and  hydrogen,  but  to 
attain  such  a  result  at  this  temperature  would  require 
many  minutes  in  the  heating  zone.  On  the  other 
hand,  this  complete  decomposition  is  realized  at 
1600°  C.  in  a  comparatively  short  reaction  period, 
due  to  the  great  increase  in  the  rate  of  decomposition 
at  the  high  temperature  over  that  at  the  lower  tem- 
perature so  that  the  shorter  time  in  the  heating  zone 
is  sufficient  for  the  complete  decomposition. 

With  any  design  of  generator  for  the  production  of 
hydrogen  by  the  direct  decomposition  of  hydrocarbon 
oils,  the  time  in  the  heating  zone  must  be  such  as  to 
favor  complete  decomposition  at  the  desired  tem- 
perature. This  temperature  has  both  a  minimum  and 
a  maximum  value  dependent  upon  the  principles  of 
thermodynamics  and  upon  practical  reasons,  respec- 
tively. The  minimum  is  that  lowest  temperature  at 
which  equilibrium  composition  represents  complete 
decomposition;  i.  e.,  about  1200°  C.,  at  which  tem- 
perature a  long  time  would  be  necessary  to  complete  the 

(24) 


reaction.  The  maximum  is  that  limited  by  economical 
design  and  practical  temperatures. 

In  Runs  6  and  7,  made  at  very  slow  rates  of  oil  feed, 
there  are  small  percentages  of  hydrocarbons  present. 
This  is  apparently  due  to  a  reversal  of  reactions  as 
in  the  theoretical  consideration  it  was  concluded  that 
if  the  rate  of  cooling  was  slow  the  reactions  would 
reverse  toward  that  equilibrium  composition  cor- 
responding to  a  lower  temperature. 

In  view  of  these  results  the  range  of  complete  de- 
composition is  limited  not  only  by  temperature  but 
also  by  definite  rates  of  oil  feed  which  have  a  maximum 
and  a  minimum  limit.  The  maximum  is  that'  rate 
at  which  the  time  allowed  for  reaction  is  just  sufficient 
for  complete  decomposition.  The  minimum  •  is  that 
rate  at  which  the  time  required  to  arrest  the  reactions 
in  the  cooling  zone  is  sufficiently  long  to  cause  a  meas- 
urable reversal  of  reactions.  For  any  temperature 
at  which  complete  decomposition  is  possible,  these 
limiting  rates  will  have  different  values. 

From  these  considerations  it  seems  that  the  direct 
decomposition  of  hydrocarbon  oils  might  become  a 
future  source  of  large  quantities  of  hydrogen,  but 
difficulties  would  be  encountered  in  the  commercial 
application  of  such  a  process.  These  obstacles  would 
consist  mainly  in  the  economical  heating  of  the  reacting 
substances  to  the  necessary  high  temperature  and  in 
the  purification  of  the  resulting  gas.  Economical 
heating  could  probably  be  attained  by  the  use  of  a 
counter-current  system.  Purification  would  be  neces- 
sary in  order  to  remove  the  oxygen  and  sulfur  com- 
pounds derived  from  the  original  oil. 

Crossley1  has  reviewed  the  commercial  hydrogen 
situation  to  date,  but  has  omitted  reference  to  the 
direct  decomposition  of  oil  as  a  possible  source  of 
hydrogen.  A  few  patents2  relating  to  such  processes 
have  been  issued. 

ILLUMINANTS 

Table  V  consists  of  data  taken  from  the  curves  of 
Fig.  VII.  These  data  show  that  it  is  possible  to  obtain 
gases  containing  equal  percentages  of  illuminants  at 
different  temperatures  by  varying  the  rate  of  oil  feed. 
At  a  given  temperature  and  rate  of 'oil  feed  a  certain 
percentage  of  illuminants  is  obtained.  Should  it  be 
desired  to  obtain  a  gas  containing  an  equal  percentage 

i  Crossley,  J.  Soc.  Chem.  Ind.,  33  (1914),  1135. 

'  Frank.  U.  S.  Pat.  1,107,926  (1914);  Ellis.  U.  S.  Pat.  1,092,903  (1914). 

(25) 


of  illuminants  at  a  higher  temperature,  it  would  be 
necessary  to  increase  the  rate  of  oil  feed;  this  is  strictly 
in  accord  with  the  theoretical  principle  of  reaction 

TABLE  V — EQUAL  PERCENTAGES  OF  ILLUMINANTS  OBTAINED  AT  DIFFERENT 

TEMPERATURES  BY  VARYING  THE  RATE  OF  OIL  FEED 
Temperatures    Oil  rate       COMPOSITIONS  OF  GASES   (PERCENTAGES) 


c. 

Cc.  per  rain. 

Ilium 

H2 

CMH2n_| 

800 
1000 

14.0 
55.0 

40.0 
40.0 

18.5 
22.0 

41.5 
38.0 

1000 
1200 

14.0 
57.0 

20.0 
20.0 

44.4 
53.7 

35.6 
26.3 

1000 
1200 
1400 

3.5 
26.5 

55.5 

10.0 
10.0 
10.0 

58.2 
66.5 
74.0 

31.8 
23.5 
16.0 

1000 
1200 
1400 
1600 

1.0 
14.0 
35.0 
50.0 

5.0 
5.0 
5.0 
5.0 

63.5 
78.5 
85.5 
87.0 

31.5 
16.5 
9.5 
8.0 

velocity  that  increase  in  temperature  increases  rate  of 
decomposition  and  hence  it  should  be  necessary  to 
increase  the  rate  of  oil  feed  (equivalent  to  decreasing 
the  time  for  reaction)  in  order  to  obtain  the  same  per- 
centage of  illuminants  in  the  resulting  gas.  However, 
gases  containing  equal  percentages  of  Illuminants 
do  not  necessarily  contain  equal  percentages  of  the 
other  constituents.  This  is  apparently  due  to  un- 
equal effects  of  change  of  temperature  on  the  various 
reactions  involved  in  the  decomposition.  With  a 
desired  percentage  of  illuminants  in  view,  then,  it 
would  be  possible  to  increase  materially  the  capacity  of 
any  oil  gas  generator  by  increasing  the  temperature  a 
hundred  or  more  degrees. 

Experimentally  it  was  found  that  a  gas  containing 
about  52.0  per  cent  illuminants  could  be  obtained  at 
800°  C.  at  a  high  rate  of  oil  feed  but  at  the  same  time 
a  large  amount  of  tar  was  produced. 

GAS    GENERATED 

Fig.  IX  consists  of  two  sets  of  curves,  one  showing 
the  gas  rates  and  the  other  the  gas  yields  for  the  various 
rates  of  oil  feed  at  constant  temperature.  The  rates 
of  gas  generation  and  yields  at  1600°  C.  are  not 
shown,  as  runs  at  this  temperature  could  not  be  main- 
tained for  a  sufficiently  long  time  to  obtain  accurate 
data,  on  account  of  the  choking  of  the  furnace  by  the 
large  amounts  of  carbon  formed. 

The  gas  rate  curves  show  that  at  constant  tem- 
perature an  increase  in  the  rate  of  oil  feed  does  not 
result  in  a  proportionate  increase  in  the  rate  of  gas 
generation  but  rather  in  a*  decreasing  ratio  of  gas 
rate  to  oil  rate.  As  a  result,  at  low  temperatures  and 
high  rates  of  oil  feed  the  rates  of  gas  generation  do  not 
show  a  material  change  over  a  considerable  range. 

(26) 


At  800°  C.  and  at  very  high  rates  of  oil  feed  the  rate 
of  gas  generation  actually  becomes  a  decreasing  func- 
tion. This  is  apparently  due  to  trie  checking  of  the 
course  of  the  reactions  by  the  insufficient  time  interval 


5      10      15      20     25     50      35    40     45      50     55     60    65 
OIL  RATE-  cc.  permin. 


1200 


5       10      15      20     25      30      35    40     45      50     55     60    65 

OIL  RATE- cc.  permin. 
FIG.  IX— GAS  CURVES 

allowed  or  to  so  exceeding  the  capacity  of  the  furnace 
that  the  oil  vapors  are  not  heated  to  the  temperature 
of  the  reaction  zone. 

(27) 


The  gas  yield  curves  indicate  that  increase  in  tem- 
perature results  in  an  increase  of  the  yield  of  gas  at 
any  constant  rate  of  oil  feed.  This  is  due  to  the  more 
complete  decomposition  of  the  hydrocarbons,  as  shown 
by  the  compositions  of  the  gases  made  at  slow  rate 
(Fig.  VII).  At  constant  temperature,  decrease  in 
the  rate  of  oil  feed  will  result  in  an  increase  in  the 
yield  of  gas  to  whatever  maximum  is  representative 
of  the  most  complete  decomposition  to  be  attained  at 
the  given  temperature.  As  stated  previously  a  de- 
crease in  the  rate  of  oil  feed  provides  the  longer  re- 
action period  necessary  for  final  equilibrium.  Since 
the  most  complete  decomposition  at  any  one  tempera- 
ture is  characteristic  of  equilibrium  composition,  a 
maximum  yield  of  gas  can  be  obtained  only  at  this 
final  stage,  although  such  yields  of  gas  can  not  be 
realized  experimentally  on  account  of  the  above- 
mentioned  reversal  of  reactions  in  the  cooling  zone. 

TARS 

Tar  yields  could  not  be  determined  with  accuracy 
in  these  runs  as  the  high  rates  of  gas  generation  in  many 
of  the  experiments  made  it  impossible  completely  to 
separate  the  tars  from  the  gases  with  the  apparatus 
at  hand.  In  general,  the  tar  yield  increased  with  in- 
crease in  the  rate  of  oil  feed  at  a  given  temperature 
and  with  a  decrease  in  temperature  at  constant  rates 
of  oil  feed.  Above  1200°  C.,  at  slow  rates  of  oil  feed, 
no  tars  were  obtained.  The  nature  of  the  tars  obtained 
at  the  various  temperatures  has  not  been  investigated. 

CONCLUSIONS 

I — The  control  of  the  composition  of  the  products 
obtained  in  the  manufacture  of  oil  gas  involves  not 
only  thermodynamics  but  also  chemical  kinetics. 

II — In  practice,  equilibrium  is  not  reached  in  the 
thermal  decomposition  of  petroleum  hydrocarbons. 
This  is  proved  by  the  fact  that  a  recirculation  of  the 
products,  under  the  same  conditions  at  which  they 
were  generated;  results  in  a  further  change  in  composi- 
tion. 

Ill — The  time  factor,  which  is  controlled  by  the 
rate  of  oil  feed,  is  just  as  important  as  are  the  other 
variables  (temperature,  pressure  and  concentration), 
as  it  has  been  found  that  the  compositions  of  the 
products  obtained  in  making  oil  gas  vary  with  the  rate 
of  oil  feed.  Hence,  from  the  standpoint  of  practical 

(28) 


operation  of  an  oil  gas  plant,  the  rate  of  oil  feed  offers 
an  easily  accessible  means  of  control. 

IV — Maximum  and  minimum  percentages  of  the 
various  constituents  in  the  products  formed  by  the 
decomposition  of  petroleum  and  petroleum  distillates 
by  heat  can  be  obtained  by  a  proper  adjustment  of 
the  variables. 

V — Petroleum  hydrocarbons  can  be  completely 
decomposed  into  carbon  and  hydrogen  only  within 
well  defined  limits  of  the  four  variables.  In  this 
investigation  the  range  of  complete  decomposition 
at  a  definite  temperature  and  pressure  was  limited 
by  definite  rates  of  oil  feed. 

VI — Oil  gases  containing  equal  percentages  of 
illuminants  can  be  produced  at  different  temperatures 
by  varying  the  rate  of  oil  feed.  Such  gas  mixtures, 
although  they  have  equal  percentages  of  illuminants, 
do  not  in  general  have  equal  percentages  of  saturated 
hydrocarbons  and  hydrogen,  i.  e.,  gases  of  equal  il- 
luminating values  are  not  necessarily  of  equal  thermal 
values. 

VII — In  an  isothermal  decomposition  of  petroleum 
hydrocarbons,  maximum  yields  of  gas  and  minimum 
yields  of  tar  are  characteristic  of  equilibrium  com- 
positions. 


(29) 


VITA 

Clive  Morris  Alexander  was  born  in  Leon,  Iowa,  on 
April  28,  1889,  and  there  received  his  public  school 
education,  graduating  from  the  Leon  High  School  in 
May,  1907.  He  entered -the  State  University  of  Iowa 
in  September,  1907,  and  graduated  from  that  institu- 
tion in  June,  1911,  receiving  the  degree  of  Bachelor  of 
Science  in  Chemistry.  At  the  State  University  of 
Iowa,  during  the  Summer  Session  of  1909,  he  had 
charge  of  the  stock  room  in  the  department  of  chem- 
istry, and  during  the  Summer  Session  of  1911  was  As- 
sistant in  Chemistry.  He  studied  at  Harvard  Uni- 
versity during  the  Summer  Session  of  1912.  The  two 
years  1911-2  and  1912—3  were  spent  in  graduate  work 
and  as  Assistant  Instructor  in  Chemistry  at  the  State 
University  of  Iowa.  Ifi  June,  1913,  he  received  the  de- 
gree of  Master  of  Science  from  the  same  institution. 
The  following  two  years,  1913-4  and  1914-5,  were 
spent  in  graduate  study  at  Columbia  University;  dur- 
ing the  latter  year  he  was  Goldschmidt  Fellow  in 
Chemistry. 


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